Airplane engine mixture control



April 23, 1946. I s D AIRPLANE ENGINE MIXTURE CONTROL Filed April 2, 1943 ENToR.

Patented Apr. 23, 1 946 SUPATENT OFFICE AIRPLANE ENGINE MIXTURE CONTROL Stanley M. Udale, Detroit, Mich; assignor to I George M. Holley and Earl Holley 7 Application April 2, 1943, Serial No. 481,549 r 1 Claim.

The object of this invention is to simplify the automatic control of the mixture ratio when the load and altitude varies in an airplane carburetor. The figure shows diagrammatically the essential elements of my invention. A is the Venturi means for magnifying the effect of the air flowing into the carburetor. The venturi A is the second stage of a main venturi A A is a number of openings in the downstream side of venturi A admitting air to the entrance to the second stage venturi A. A is a third venturi discharging into the throat of the second stage venturi A. A i a fourth stage venturi discharging into the throat of the third stage venturi A By this means the turbulence existing in the main venturi A is not transmitted to the metering venturi A and a large multiplication is obtained which is not sensitive to the eddies and turbulence in the main entrance. As the air to an airplane carburetor is drawn in from in back of the engine propeller,

it enters in a highly turbulent condition.

The pressure in the chamber B is maintained at the pressure at A as modified by a small leak past valve T. The pressure or rather the depression in chamber C is that existing in the throat of the smallest of the group of three concentric venturis A A and A. The difference in pressure between B and C is the force acting on the diaphragm D which forms the flexible wall between the two chambers. The fuel chambers E and F control the fuel admission valve G. The

- two chambers E and F are separated by a diaphragm H. An adjustable needle valve J controls the communication of the fuel between the two fuel chambers E and F.

The control of the needle valve J is the subi'ect matter of this patent application. A chamber K communicates with the suction created by the Venturi systemv A. A chamber L communicates with the pressure side of the Venturi system. These two chambers are separated by a diaphragm M, the movement of which controls the lateral movement of a cam N. The rotary movement of the camN is controlled by the barometric element 0 whichacts through the lever P which rotates the square shaft Q. The two opposing small diaphragms R and S are each subjected to the pressure in chamber F by the equalizing pipe X, so that the needle J can be moved easily. The engagement between" the needle J and the cam N is secured by means of two steel balls Y and Z, one of which Z, is, spring loaded. A needle valve T adjusts the pressure difierence between the chambers B and C. A similar valve, needle valve U adjusts the pressure difference between the chambers K and L. A passage V connects the outlet from the needle J with the fuel chamber E and with the spring loaded valve W which can be conveniently located anywhere in the air inlet to the engine.

Operation Assume that the engine is operating with the throttle partlyopen, as shown. Then there is a circulation of air through the venturis A, A and A producing a depression in the throat of the venturi A which acting on the diaphragm D causes the valve G to open admitting fuel. The circulation of air as shown by the arrows'is a measure of airflow. The flow of fuel past needle J produces a pressure diiference between the chambers E and F due to the restriction imposed by the valve J. This valve J is controlled by the sliding and rotating cam N. This cam N is rotated by the barometric responsive lever P and is translated by the diaphragm M. This diaphragm M responds to the airflow like the diaphragm D responds to airflow. Hence, at any given altitude, the position of the valve J is determined by the air flow and by the altitude. 'Every position 01' the valve J corresponds to a definite mixture ratio. As we know or can ascertain the exact amount of fuel that the engine needs at any specific air flow and at any specific altitude, we can grind the cam N at each altitude position to give just exactly the right fuel-air ratio required as the airflow varies. In other words, there are an infinite number of cam surfaces, one for each altitude, which being assembled together make a surface. This complex cam controls the mixture ratio so as to respond to the variables, altitude and load.

What! claim is: In a carburetor having an air entrance, a venturi associated therewith, a first air suction chamber connected to the throat of said venturi, a first air pressure chamber connected to the high pressure side of said Venturi system, a diaphragm therein forming a wall common to both chambers so that it is responsive to the pressure difference created by said venturi, a fuel entrance, a valve controlling said entrance, a first fuel chamber, a diaphragm therein, a restricted fuel outlet from said first fuel chamber, a passage leading from said restricted outlet'to said engine, a second fuel chamber communicating with said outlet, said diaphragm being located between said- 2 ammo-n sir and fuel diophresms insetber with said tuel entrance valve for the purpose described, mixture.

ratio controlling means tor said carburetor comprising a second air suction chamber communicating with the depression created by said Venturi system, a second air pressure chamber communieating with high pressure side 01 said Venturi system, a. diaphragm between said chembers responsive to the depression erected by said Venturi system, a rotatable com adopted to be moved exioils in response to the movement or said last mentioned diaphragm. barometric means responsive to the atmospheric pressure for rotating said com, o fuel restricting means adapted to move in said restricted iuel outlet and to be moved by said cam tor controlling the flow oi. loci from said hilh liressure fuel chamber to said iuel outlet throush said restricted outlet.

- sum? M. mam. 

